The present invention relates generally to a tree harvesting machine attachable to a vehicle, and more particularly, to a hydraulically controlled shear assembly utilized with such a tree harvesting machine.
The present invention concerns a tree harvesting machine generally shown and described in Moser et al U.S. Pat. No. 3,842,872 entitled "Delimber Assembly For Tree Harvesting Machines", issued Oct. 22, 1972, and Gutman et al U.S. Pat. No. 3,669,161 entitled "Drive Mechanism For Tree Harvesters", issued June 13, 1972. Both of the above are assigned to the assignee of the present invention.
A shear assembly is employed with a tree harvesting machine to sever trees from the ground. Typically, the shear assembly is situated at the lower end of the harvester head so that a tree may be cut at its base. The shear assembly is actuated by hydraulic jacks having flexible hydraulic lines leading therefrom to a source of fluid under pressure and a control circuit disposed on the vehicle carrying the harvester head.
Because the shear assembly is employed near the ground, in prior art constructions the hydraulic lines may be pinched or severed when trapped between the ground and a portion of the harvester head or struck by tree parts or the like. The hydraulic lines may also be severed if they are caught between the movable portions of the shear assembly when the shear assembly is closed. Because the hydraulic lines are connected to moving parts, they cannot be suitably reinforced since they must be capable of flexing in response to the movements of the hydraulic jacks. In addition, the hydraulic lines, if unprotected, may be damaged by debris packing or freezing around the lines during inactive periods and during subsequent startup.